Method for forming sockets

ABSTRACT

A process for forming, at the end of a pipe fabricated from a synthetic resin material, a socket having external ribs, beads, or the like, extending in cross-sectional planes or helically, which comprises the insertion of a temperature-controlled mandrel in the end of an initially-heated pipe, simultaneously imparting a rotary motion to the mandrel as it is axially advanced and, upon cooling of the pipe end, withdrawal of the mandrel with further rotary motion thereof.

Jan. 4, 1972 G. OSTERHAGEN EI'AL 3,632,732

METHOD FOR FORMING SOCKETS INVENTORS GERHARD OSTERHAGEN FRIEDHELM KREBSBACH WALDEMAR WISSINGER Filed Oct f 21 1969 United States Patent 3,632,732 METHOD FOR FORMING SOCKETS Gerhard Osterhagen, Driesch, and Friedhelm Krebsbach and Waldemar Wissinger, Siegburg, Germany, assignors to Dynamit Nobel AG, Troisdorf, Germany Filed Oct. 21, 1969, Ser. No. 868,180

Claims priority, application Germany, Nov. 9, 1968, P 18 08 110.2 Int. Cl. B29d 1/00; B29c 17/00 U.S. Cl. 264-312 6 Claims ABSTRACT OF THE DKSCLOSURE A process for forming, at the end of a pipe fabricated from a synthetic resin material, a socket having external ribs, beads, or the like, extending in cross-sectional planes or helically, which comprises the insertion of a temperature-controlled mandrel in the end of an initially-heated pipe, simultaneously imparting a rotary motion to the mandrel as it is axially advanced and, upon cooling of the pipe end, withdrawal of the mandrel with further rotary motion thereof.

BACKGROUND OF THE INVENTION Conventionally, the processes employed for forming sockets on smooth pipes, i.e., pipes having a constant wall thickness, have generally included heating the end of the pipe and then forcing same over an expanding mandrel corresponding, in its outer dimensions, to the internal dimensions of the socket to be formed and provided with smooth external surfaces. Methods of this type, however, cannot be employed for producing sockets on pipes fabricated from synthetic resin materials, which pipes include external ribs, beads, or the like, primarily because the sections of pipe disposed between the beads, which sections exhibit a thickness substantially less than that of the beads themselves, would be compressed, with the resulting formation of wrinkles, creases, or folds. Moreover, the known processes whereby the end of the pipe on which the socket is to be formed is pulled over the mandrel, as well as those attempts to preclude the formation of undesirable wrinkles by providing external support, have not afforded the results desired.

It has also been suggested that sockets of the type described hereinabove could be successfully formed by the use of an expanding mandrel composed of a plurality of separable segments. These eiforts have been similarly unsuccessful and are, moreover, extremely expensive and complex in operation.

Accordingly, it is an object of the present invention to provide a novel method for producing sockets with external ribs, beads, or the like on the ends of pipe fabricated from a synthetic resin material, which sockets are generally free from undesirable wrinkles or creases in the sections between the beads.

Further, it is an objective of the present invention to provide a method which effectively eliminates the disadvantages inherent in the conventional processes for performing a similar function.

Moreover, it is an objective of the present invention to provide a method for forming sockets having external ribs, beads, or the like on the ends of pipes fabricated from a synthetic resin material, which process is relatively simple and inexpensive, both from the standpoint of the production of the apparatus required and the operation thereof.

SUMMARY OF THE INVENTION The aforementioned objectives are accomplished, in ac- 3,632,732 hatented Jan. 4, 1972 cordance with the present invention, by providing a temperature-controlled mandrel which has an external configuration corresponding to that of the inner contour of the socket to be formed and by introducing the mandrel nto the end of the pipe, which has been initially heated, imparting a rotational motion to the mandrel as it is advanced in the axial direction of the pipe. When the mandrel has been advanced to the full extent of its axial displacement, the rotary motion thereof is terminated; thereafter the pipe end is cooled internally and/or externally and the mandrel is withdrawn from the formed socket again having a rotary motion imparted thereto.

In accordance with one embodiment of the present invention, wherein a socket is formed having helically-extending ribs, beads, or the like the rotary motion of the mandrel is in the direction of the pitch of the helical beads, as viewed from the mandrel side of the socket.

The novel process according to the present invention can be employed for cylindrical as well as com'cal expandlng operations. By way of example, the novel process according to the present invention produced flawless sockets formed on PVC pipes having an internal diameter of 500 mm, wall thicknesses of 5 and 6 mm., as well as external ribs having a height of 15 and 20 mm., extending helically at a pitch of about 100 mm., utilizing peripheral mandrel speeds in the range of 40-80 m./min. The temperatures of the mandrel ranged between about to C.; in this regard, it was found to be advantageous to utilize a mandrel heated to a temperature higher than that corresponding to the softening point of the material.

The novel apparatus contemplated by the present invention includes an expanding mandrel which, when viewed from the end of the pipe to be expanded, exhibits, successively, a cylindrical guide member having a crosssectional dimension slightly smaller than the internal diameter of the pipe, and, adjacent thereto, a section having a larger cross-sectional dimension, corresponding to the internal cross-sectional dimensions of the socket to be formed. The guide member serves to insure an accurate centering of the mandrel and, additionally, to prevent the creation of wrinkles in the heated, but as yet unexpanded, pipe section. The length of the guide member, which normally need not be temperature-controlled, depends upon the dimensional configuration of the socket to be formed.

At least one cutting blade is provided for the purpose of trimming the edge of the socket simultaneously with the forming thereof. The cutting blade, which may be provided at the end of the mandrel opposite the pipe or on a ring mounted adjustably upon the mandrel, projects outwardly beyond the mandrel or ring to such an extent as to insure a clean trimming of the front face of the formed socket. It is also within the contemplation of the present invention to provide a plurality of cutting blades, in which case these would advantageously be distributed, at equal spacing, over the circumference.

In order to securely fix the more or less elastic and flexible pipes, fabricated from synthetic resin material, with respect to the relatively high torques generated by the rotating expanding mandrel, the mandrel, according to the present invention, may be constructed with a central, axial, rod-shaped cylindrical extension at the end thereof facing the pipe end and a supporting mandrel may be disposed on this extension, displaceable and rotatable with respect to the extension and adapted to the internal diameter of the pipe to be expanded. Thus, it is possible to apply the pressure necessary for securing and retaining the pipe, by means of the customary, external clamping devices, while precluding the formation of an undesired depression in the pipe. On the other hand, the displaceability and rotatability of the expanding mandrel is not inhibited by the contemplated support arrangement.

3 BRIEF DESCRIPTION OF THE DRAWING The aforementioned objectives, features and advantages of the present invention will become more readily apparent from a consideration of the detailed description hereinbelow, when considered in conjunction with the accompanying drawing, diagrammatically illustrating one embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWING According to the illustrated embodiment, a pipe '1, fabricated from a synthetic resin material, includes external reinforcing ribs 2 extending thereabout in a helical fashion. The pipe *1 is widened at its end to form the socket 3. An expanding mandrel 4, which is capable of being heated and/or cooled by way of the connecting members 13, includes a conical section 5 and a guide member 6 which, according to the illustrated embodiment, is cylindrical in configuration. The end 7 of the socket 3 is conically widened by means of the terminal ring 8 disposed on the mandrel 4, for example, to facilitate the introduction of another pipe section (not shown) into the formed socket 3 of pipe 1. Cutting blades 9 are affixed upon the ring 8 for purposes of trimming the rim of the socket 3 or 4 leveling the front face thereof.

The expanding mandrel 4 is coupled with a shaft 10 which is driven by means of a drive mechanism (not shown), which driven shaft 10 imparts a rotary motion to mandrel 4. The drive mechanism (not shown), the shaft 10 and, therefore, the mandrel 4 are disposed upon a slide 11, thereby facilitating reciprocation thereof in the axial direction of the pipe 1, as indicated by the double arrow extending the direction of the pipe axis.

External spray units 12 are provided for the purpose of cooling the socket 3 after it has been formed. The pipe 1 is secured in its position by means of clamping jaws 14. In the interior of pipe 1 in the region of the clamping jaws 14, a supporting mandrel 15 is provided, supported upon an extension .17 of the mandrel 4. The extens1on17 serves to loosely guide and support the supporting mandrel 15 for rotation and displacement relative thereto. Supportmg mandrel 15 includes a conical section 16 to facilitate 1nsertion thereof into the end of pipe 1.

Element 18, illustrated schematically in the drawing, serves to fix the position of supporting mandrel 15 relat ve to the extension 17 prior to the beginning of the forming operation such that when the supportingmandrel 15 1s inserted into the pipe 1, it is fixed in position therein and released upon the onset of the rotary motion of mandrel 4.

The socket-forming operation, contemplated by the illustrated embodiment, proceeds as follows: with the expanding mandrel 4 retracted toward the left-hand position, as viewed in the drawing, the pipe 1 1s placed 1n position between the clamping jaws 14. The supporting mandrel 15 in this position, is disposed between the clamping jaws 14 on the right-hand end of the extension 17 and is retained in position by means of the blocking means 18. The mandrel 4 is then heated and is adjusted to the desired operating temperature. In the same manner, the end of the pipe 1 is heated by means of the heating unit 12.

By means of the drive mechanism (not shown), the shaft 10 and, accordingly, the mandrel 4, are set into rotary motion; the blocking member 18 is automatically released. The rotating mandrel 4 is now inserted into the heated end of the pipe 1 and the pipe end is appropriately expanded.

After the termination of the expanding step, 1.e., when the mandrel 4 has arrived at its right-hand terminal position, the rotary motion of the mandrel 4 1s termmated.

The expanded pipe end 3 is then cooled by switching the mandrel 4 from a heating mode to a cooling mode by means of the connecting members 13-. The operating medium for the heating and cooling device may be hot and cold water, or, as an alternative, steam and cold water. In order to increase the cooling rate, the socket 3 can be cooled additionally with air or water by means of the device 12.

After the socket 3 has been cooled sufliciently, the mandrel 4 is again set into rotary motion and is withdrawn from the socket 3; the pipe 1 is removed from the clamping jaws 14 and a new pipe 1 is secured therein for a subsequent operation.

While the present invention has been disclosed with reference to the specific details of but a single embodiment, it is to be understood that the scope of the invention is not limited to the specific details illustrated, but is susceptible to numerous changes and modifications as would be apparent to one with normal skill in the pertinent technology.

What is claimed is:

1. A process for forming a socket at an end of a pipe fabricated from a thermoplastic synthetic resin material and having external ribs, beads, or the like extending thereabout in cross-sectional planes or helically, comprising the steps of:

heating the end of the pipe,

inserting a temperature-controlled mandrel into said end of said pipe, said mandrel having an external configuration corresponding to the internal configuration of the socket to be formed,

forming said socket by advancing said mandrel axially into said end of said pipe to a desired depth while simultaneously imparting a rotary motion to said mandrel,

cooling the formed socket, and

withdrawing said mandrel from the formed socket while simultaneously imparting a rotary motion to said mandrel.

2. A process according to claim 1, wherein the initial rotary motion of said mandrel is terminated when the axial advance thereof is completed, said rotary motion being initiated again when the withdrawal of said mandrel commences.

3. A process according to claim 2, wherein said cooling of the formed socket is effected from the interior thereof.

4. A process according to claim 2, wherein said cooling of the formed socket is effected from the exterior thereof.

5. A process according to claim 2, wherein said cooling of the formed socket is effected both from the interior and the exterior thereof.

6. A process according to claim 2, wherein said pipe has external ribs, beads, or the like extending helically thereabout and said rotary motion of said mandrel is effected in the direction of the pitch of said helical ribs, beads, or the like.

References Cited UNITED STATES PATENTS 3,254,147 5/ 1966 Nakada 264296 X 3,264,383 8/1966 Niessner "264--209 X 3,293,018 12/1966 Doty 264-310X ROBERT F. WHITE, Primary Examiner R. R. KUCIA, Assistant Examiner US. Cl. X.R. 264-322 

